The instant invention relates to electrostatic copying machines, and more particularly to a cleaning device for cold pressure fusing rollers in such machines.
Conventionally, in the direct or indirect electrostatic copying process, for the fixing of a developed image formed of a proper toner on a permanent record carrier, various fixing processes may be used. According to a known fixing process, the permanent record carrier (such as a paper sheet) is passed between a heated fixing roller and a pressure roller which is in engagement with the fixing roller. During this step the powder of the toner image is melted on the sheet and is caused to adhere thereto. This process, however, still has certain drawbacks. A portion of the toner sticks to the circumferential surface of the fixing roller which contacts the toner image; these adhered residues then are transferred to the consecutive record carriers, thus causing soiling thereof. In case the temperature of the fixing roller is too low, unmelted powder adheres thereto and is pressed, in an offset-like manner, onto the successive record carriers. If, on the contrary, the temperature of the fixing roller is too high, melted powder may adhere thereto and again, soil the successive sheets. In order to prevent such an offset soiling of the permanent record carriers, it is necessary to carefully control the fixing temperature. Such a control of the fixing temperature, however, is fraught with difficulties.
More recently, due to the availability of new toners, another fixing process has been introduced wherein the toner image is fixed without the use of heat by means of generating a sufficiently high pressure between the two rollers. In this process too, after the pressure fixing, a certain quantity of toner remains on the cylindrical surface of the fixing roller which had contacted the toner image; these toner portions have to be removed as well, since the residual toner adhering to the fixing roller would again lead to the above-noted offset soiling of the record carriers.
It is a common practice to provide a device to remove the excess toner accumulated on the cold pressure fixing rollers, one such device being a scraper blade. However, there are certain problems attendant with the use of scraper blades, such as annoying squeaks and insufficient wear characteristics. In those fixing roller assemblies where the rollers are skewed, i.e. cross each other, there is posed an additional problem of conforming the scraper blade to the surface of the roller, making skewed fixing rollers especially difficult to clean. The foregoing problems are all overcome by the instant invention.